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Aerobic Respiration
Section
9:2
Overview
• Krebs Cycle: In the presence of
O2, Pyruvic Acid oxidizes, the
reduction of NAD+ to NADH, and
FAD to FADH, and a small
amount of ATP is made.
• Krebs or the ETC. will only occur
if, CO2, H2O and O2 are ALL
present.
Aerobic Respiration – Oxygen
Present
• Occurs in the mitochondria of
eukaryotes and the cytosol of
prokaryotes.
• Pyruvic acid, from Glycolysis,
diffuses in from the cytosol to the
mitochondrial matrix.
–The space inside the inner
membranes
inner compartment
outer compartment
cytoplasm
outer
mitochondrial
membrane
inner
mitochondri
al membrane
(see next slide)
Fig. 7.5a, p. 114
Aerobic Respiration – before
KC
• Pyruvic acid joins with
coenzyme A (CoA), no
carbons, to form acetyl
CoA – 2 carbons
• CO2 is lost in this process
and NAD is reduced to
+
NADH and H .
Krebs Cycle
• A biochemical pathway that
breaks down acetyl CoA
producing CO2, NADH, FADH,
and ATP and Citric acid.
• 5 steps to the Krebs cycle
Step 1
• The 2-carbon acetyl CoA
combines with a 4-carbon
compound, oxaloacetic acid,
to form a 6-carbon molecule,
citric acid
• This step regenerates coenzyme A
PREPARATORY
STEPS
pyruvate
coenzyme A (CoA)
NAD+
(CO2)
NADH
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate H O
2
NADH
H2O
NAD+
malate
NAD+
H2O
isocitrate
NADH
fumarate
FADH2
FAD
a-ketogluterate
CoA
NAD+
NADH
succinate
CoA
succinyl–CoA
ATP
ADP + phosphate
group (from GTP)
Fig. 7.6, p. 115
Step 2
• Citric acid releases a CO2 and
a hydrogen to form a 5-carbon
compound
+
+
• NAD accepts an H to become
+
NADH and H .
PREPARATORY
STEPS
pyruvate
coenzyme A (CoA)
NAD+
(CO2)
NADH
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate H O
2
NADH
H2O
NAD+
malate
NAD+
H2O
isocitrate
NADH
fumarate
FADH2
FAD
a-ketogluterate
CoA
NAD+
NADH
succinate
CoA
succinyl–CoA
ATP
ADP + phosphate
group (from GTP)
Fig. 7.6, p. 115
Step 3
• The 5-carbon compound
releases CO2 and H+ to form a
4-carbon compound.
+
• NAD is reduced again to
NADH and One molecules of
ATP is made
PREPARATORY
STEPS
pyruvate
coenzyme A (CoA)
NAD+
(CO2)
NADH
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate H O
2
NADH
H2O
NAD+
malate
NAD+
H2O
isocitrate
NADH
fumarate
FADH2
FAD
a-ketogluterate
CoA
NAD+
NADH
succinate
CoA
succinyl–CoA
ATP
ADP + phosphate
group (from GTP)
Fig. 7.6, p. 115
Step 4
• The 4-carbon compound
releases hydrogen
• The hydrogen forms with
+
FAD to form FADH2. FAD
is another electron
acceptor.
PREPARATORY
STEPS
pyruvate
coenzyme A (CoA)
NAD+
(CO2)
NADH
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate H O
2
NADH
H2O
NAD+
malate
NAD+
H2O
isocitrate
NADH
fumarate
FADH2
FAD
a-ketogluterate
CoA
NAD+
NADH
succinate
CoA
succinyl–CoA
ATP
ADP + phosphate
group (from GTP)
Fig. 7.6, p. 115
Step 5
• The 4-carbon compound
releases a hydrogen to
REFORM oxaloacetic
acid
+
• NAD is reduced again to
+
NADH and H
PREPARATORY
STEPS
pyruvate
coenzyme A (CoA)
NAD+
(CO2)
NADH
CoA
Acetyl–CoA
KREBS CYCLE
CoA
oxaloacetate
citrate H O
2
NADH
H2O
NAD+
malate
NAD+
H2O
isocitrate
NADH
fumarate
FADH2
FAD
a-ketogluterate
CoA
NAD+
NADH
succinate
CoA
succinyl–CoA
ATP
ADP + phosphate
group (from GTP)
Fig. 7.6, p. 115
• Glycolysis, produces 2 NADH and 2
pyruvic acid, 2 ATP.
• One molecule of glucose from
glycolysis needs 2 turns of the Krebs
to produce:
• Summary: 10 NADH, 2 FADH, 4 ATP, 4
CO2. The 10 NADH and 2 FADH (both
energy molecules) will drive the next
stage of cellular respiration in the
Electron Transport Chain.
Krebs Cycle conclusion
• Location – Mitochondrial Matrix (space
inside the inner membrane)
• Function – Produce CO2, ATP, NADH,
FADH and Citric Acid.
• Reactants – Pyruvic Acid,Acetlyl-CoA,
Oxaloacitic Acid, NAD, FAD, ADP and
C0enzyme A.
• Products – CO2 NADH, FADH, ATP and
Citric acid.
The Electron
Transport Chain in
Cellular Respiration
Cellular Respiration
• The process that releases
energy by breaking down
glucose and other food
molecules in the presence
of oxygen.
Electron Transport Chain
• A chemical reaction that uses
high energy electrons made in
the Krebs cycle to convert ADP
into ATP.
• Aerobic – means with oxygen
• Anaerobic – means without
oxygen
Electron Transport Chain
• ATP is produced when NADH
and FADH2 release hydrogen
atoms, regenerating NAD+ and
FAD+.
• This occurs along the lining of the
inner membranes of the
mitochondria.
Steps of ETC
• 1. Electrons from the
hydrogens atoms of
NADH and FADH are
passed along a series of
molecules, losing energy
along the way.
• 2. This energy pumps protons
from the matrix to the other
side of the membrane.
• This creates a concentration
gradient across the inner
membrane of the mitochondria.
OUTER COMPARTMENT
NADH
INNER COMPARTMENT
Fig. 7.7a, p. 116
• 3. This
high proton concentration
is what drives chemiosmosis (
ATP production) into the inner
membrane. ATP synthase is
located in the inner membrane.
ATP is made as protons move
down their concentration gradient
in the mitochondria.
Oxygen’s Role
• Oxygen is the final electron acceptor,
accepting electrons from the last molecule
in the ETC.
• This allows ATP to continue to be
synthesized.
• Oxygen also accepts the hydrogen atoms
from NADH and FADH.
• This combination of electron, hydrogens
and oxygen forms WATER!!!!! O2 + e+H- = H2O
ATP
NADH
INNER
COMPARTMENT
ADP
+
Pi
Fig. 7.7b, p. 116
Energy Yield
• Per molecule of glucose, 36 ATP’s
are produced. 2 in Glycolysis, and
approximately, 4 in Krebs and 30 in
ETC.
• C6H12O6 + 6O2  6CO2 + 6H2O +
energy
1 Pyruvate from
cytoplasm enters
inner mitochondrial
compartment.
OUTER COMPARTMENT
NADH
acetyl-CoA
Krebs
Cycle
NADH
NADH
3 NADH and
FADH2 give up
electrons and
H+ to membranebound electron
transport systems.
ATP
2 Krebs cycle and
preparatory steps:
NAD+ and FADH2
accept electrons and
hydrogen stripped
ADP
from the pyruvate.
+ Pi
ATP forms. Carbon
dioxide forms.
INNER COMPARTMENT
4 As electrons
move through the
transport system,
H+ is pumped to
outer compartment.
ATP
ATP
ATP
5 Oxygen
accepts
electrons,
joins with H+
to form water.
free oxygen
6 Following its gradients, H+ flows back
into inner compartment, through ATP
synthases. The flow drives ATP formation.
Fig. 7.5b, p. 114
Krebs Cycle and ETC.
• Both the Krebs Cycle and the Electron
Transport chain can not proceed without
the presence of
• O2
• H2O
• CO2
Conclusion of Electron Transport
Chain
• Location – Lining of the inner
membrane of the mitochondria.
• Function – Produce ATP and water
• Reactants – NADH, FADH, ADP and
O2.
• Products – NAD, FAD, ATP and
Water
Order of processes in
Cellular Respiration.
•1. Glycolysis
•2. Krebs cycle
•3. Electron Transport
Chain
# of carbon atoms in
compounds
•
•
•
•
•
•
•
•
•
•
CO2 – 1
RuBP – 5
Glucose – 6
Oxaloacitic Acid – 4
Acetyl Co-A – 2
Pyruvic Acid – 3
Citric Acid – 6
Lactic Acid – 3
Ethyl Alcohol – 2
Co-enzyme A - 0
PGA - 3
PGAL - 3